One aim of these studies is to evaluate the changes in body organ water and albumin compartments and to assess their contributions to homeostasis and particularly to the prevention of pulmonary edema in stress states. Methods for quantitating the water and albumin compartments are being developed for use in vitro. For evaluating pulmonary capillary permeability in vivo an indicator dilution method is being combined with an interactive computer. A technique for separately assessing permeability and surface area of the pulmonary capillary bed appears to be successful.